Method and apparatus for optical projection of deformation images

ABSTRACT

The optical projection of information stored in a relief image such as a pattern of surface deformation of a light reflecting medium is accomplished by a projector which images on a screen the foci of either of the two sets of mirrors produced by the curved surfaces of the deformations. The hollows or concave mirrors provided by the bottoms of the deformations have their foci in front of the recording and when imaged on a screen by the projection optics provide a bright line image on a light background. The convex mirrors at the edges of the deformations have their foci (virtual) located to the rear of the recording and when imaged on the screen by the projection optics provide a dark outline of the deformations on a light background. In the embodiment illustrated, the projector is a reader and is provided with a back projection screen at the same end of the reader as the recording to be projected and the projection path includes suitable mirrors for reversing the direction of the projected light.

United States Patent Burgess et al.

[54] METHOD AND APPARATUS FOR OPTICAL PROJECTION OF DEFORMATION IMAGES [72] lnventors: James F. Burgess; Robert F. Kopczewski;

John M. l'loleman, all of Schenectady, N.Y.

[73] Assignee: General Electric Company [22] Filed: Dec. 20, 1968 [21] Appl. No.: 785,582

[52] U.S.Cl. ..353/67 [51] Int. Cl. ..G03b2l/06 [58] FieldofSearch ..353/65,66, 67; 340/l73TP;

355/9; 350/l6l, I67; l78/6.6 TP, 5.4 BD, 7.5 D

[56] References Cited UNITED STATES PATENTS 2,843,009 7/1958 Stevens ..353/67 3,166,625 l/l965 Brumley ....350/l67 3,178,993 4/1965 Ferris et al.... 350/167 3,238,296 3/1966 Nelson et al.. 178/75 D 3,044,358 6/1962 Glenn ....350/l6l 3,078,338 2/1963 Glenn ..350/l6l 3,679,299 July 25, 1972 57] ABSTRACT The optical projection of information stored in a relief image such as a pattern of surface deformation of a light reflecting medium is accomplished by a projector which images on a screen the foci of either of the two sets of mirrors produced by the curved surfaces of the deformations. The hollows or concave mirrors provided by the bottoms of the deformations have their foci in front of the recording and when imaged on a screen by the projection optics provide a bright line image on a light background. The convex mirrors at the edges of the deformations have their foci (virtual) located to the rear of the recording and when imaged on the screen by the projection optics provide a dark outline of the deformations on a light background. In the embodiment illustrated, the projector is a reader and is provided with a back projection screen at the same end of the reader as the recording to be projected and the projection path includes suitable mirrors for reversing the direction of the projected light.

5 Claim, 6 Drawing figures PATENTEDJum m2 SHEET 1 OF 3 26' I 23 /e I jhvent'or-s:

James F? Burgess, Robert F. K opczewskf John MJVo/eman, y 2 5214.4

The/r Attorney.

PATENTED L I912 3.679.299

SHEEI 2 0F 3 d #26: d Inventor-s:

James F. Burgess,

Robert F. K opczews/w',

do/m M No/emdn,

b f wlh y Their Attorney.

BEST AVAILABLE COPY METHOD AND APPARATUS FOR OPTICAL PROJECTION OF DEFORMA'IION IMAGES The present invention relates to an improvedmethod and apparatus for optically projecting information storedassurface deformations of a recording medium.

Methods of recording information in the form of apattern of surface deformations in a thermoplastic recording medium have been developed. In these methods, the deformations may be formed by the forces resulting from an electric charge pattern which may be established, for example, by an electron beam'or by a precharged photoconductive material associated with the thermoplastic layer. Methods of this type are further described and claimed, respectively, in U.S. Pat. No. 3,ll3,l78--Glenn, Jr., granted Dec. 3, 1963 and U.S. Pat. No. 3,291,601-Gaynor, granted Dec. 13, I966, respectively.

The information contained in recordings of'the above type frequently have been read out or reproduced optically by a projection'system making use of a light mask which blocks light undeviated by the deformation pattern. These systems have worked satisfactorily but have some limitations which are inherently imposed by the nature of the optical readout. For example, efficiency tends to be limited as a resultof the blocked undeviated light and the resolution tends to be limited by the unwanted diffraction that takes place at the masking system. Also, since the deformed medium itself is focused on the image or output area, dirt or other imperfections on the medium are clearly reproduced in the image area.

In accordance with an'important aspect of the present invention, the reflective recording medium is illuminated by collimated or nearly collimated light and the plane of the foci of the mirrors formed by the deformations are focused on the image area. In a typical deformation recording, the relief image elements each form a concave curvature or mirror at the center of the depression and a convex curvature or mirror at either edge of the image element. The foci of the mirrors produced .by the convex curvatures at the edges of the-deformations appear to lie behind the plane of the'medium and those produced by the concave lenslets appear to lie in a plane in front of the recording medium. The present invention contemplates a method and apparatus in which either one of these sets of foci are focused on the image area.

The features and advantages of the present invention as well as a better understanding of it will be obtained by a consideration of the following detailed description taken in'connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawing:

FIG. 1 is a side elevational view, with side'removed, of a projector embodying our invention;

FIG. 2 is a top view, with top broken away, of the projector shown in FIG. 1;

FIG. 3 is a front end elevational view of the projector of FIG. 1;

FIG. 4 is a schematic representation of the optical'system of the projector of FIG. 1;

FIG. 5 is aschematic representation of the control of the light output by the optical system of FIG. 4; and

FIG. 6 is a schematic view of a recording'useful in the 60 present invention.

A slide projector embodying the present invention and suitable for carrying out the method of the present invention is illustrated in the drawing in which a generally rectangular cabinet 10 is provided for housing an optical system and supporting, at one end thereof, as shown in FIG. 3, an adjustable picture or slide mount 11 for carrying the recording medium and a back projection screen 12 which provides the image or output area to be viewed by the observer. The projector includes a source of illumination, such as a projection lamp 13, 70

which in the illustrated embodiment is located off the projection axis and light emanating therefrom is condensed by condensing lens 14 and limited by an aperture plate 15 so that it impinges on an off axis tilted mirror 16. Light from the mirror also operates as a collimatinglens, to illuminate the reflective recordingmedium carried by the slide assembly 11 with:sub-

course, be necessary in order to maintainitheproper imaging of the output to adjust the position of the slide with respectto theprojection lens 17. This is accomplished'by thumb screw 21. Lens 22 (FIG. 4) may be included-in the projection path if. additional magnification is desired.

As indicated above, magnificationmay be controlled by adjusting the position of the mirrors l8'and 19. These mirrors are carried by common supports 23 which are moveable along the guides -24-andactivated by the lead screw 25 andcrank 20. Adjustmentof'the mirrors, ofv course, requires adjustment of the slide holder to bring the image .in'focus on the screen'l2.

As shownin FIG. 6, a typicalrecording medium-includes a substrate 26, a thermally deformable plastic layer 27'which may also include aphotoconductingv agent,.and an overlying metal film 28 which is sufiiciently thinrto be-deformedby the forces generated .inthe thermoplastic inaccordance withathe charge pattern when the thermoplastic is heated, but which:

gess application Ser. No. 418,339, filed Dec. 14, I964, now

U.S. Pat. No. 3,415,68l, granted Dec. 10, 1968,.andassigned to the assignee of the present invention.

As apparent from the consideration ofFIG. 5, the projector ofthe present invention makes use of the same lens assembly 17 for both projection and for collimating light from the source l3'so that the reflecting surface of the recording medium is illuminated by essentially parallel light..lt will be'understood that in the broader aspects of the presentinvention'it is possible to utilize a separate lens alongside the projection lens :or an annular lens surrounding the projection lens. A'lso, anon-axis beam-splitter between thev recording andtheprojection lens 17 may be used for the purpose of illuminating the recording with substantially collimated light.

FIG. 5 shows schematically how the fociof the mirrors formed by the deformation recording lie in planes which are in front of the recording medium for concave curvaturesonfithe face of therecording and behind the plane of-the medium'for the convex curvatures occurring atthe edges of each'deformation. FIG. 5 also shows schematically how thedeformations form mirrors which control the projected light to produce image areas which are respectively brighter and darker'than the background. When the projector is adjusted-t0 image the foci due to the concave mirrors on the image area, i.e., plane Cis imaged on'the screen, recorded letters; fonexample, appear essentially in dark outline withbright centers. This is illustrated at C in FIG. 5(b). This has beenreferred to'as'the image of best resolution. When thefoci due to the convex curvature appearing at the edges of the deformations are imaged on the'image area (i.e., plane 8 is imaged on the screen) the image is darker in the center with lighter surrounding outline. This is illustrated at B in FIG. 5(b). This image has been referred to as the image of best contrast.

Fromthe foregoing detailed description, itis apparent that the present invention provides an improved method of projecting images contained in deformation recordings in which the plane of the foci of the lenslets produced by the deformation is imaged on the image plane rather thanthe mediumitself, such as occur in Schlieren optical systems. It is also apparent thatthe present invention-provides an improved projecting apparatus for carrying out this method.

What we claim as new and desire to secure' by Letters is reflected through the projection lens assembly 17, which Patent of the'United States is:

1. A method of projecting information stored in a recording medium as a pattern of surface deformations including reflective surfaces with substantially similar deformations therein forming concave and convex mirrors, said concave mirrors having foci in planes in front of said medium and said convex mirrors having foci in planes behind said medium, said method comprising illuminating the reflective surface of said medium with substantially parallel light and imaging the planes of said foci of either said concave or said convex mirrors on an image area.

2. A projection system for projecting an image of information stored on a recording medium as a pattern of surface deformations, said recording medium having a reflective surface with substantially similar surface deformations which form concave and convex mirrors said concave mirrors having foci in planes in front of said medium and said convex mirrors having foci in planes behind said medium said system comprising means for supporting the recording medium, means directing substantially collimated light to the reflecting surface, a projection lens positioned along the path of light reflected from the surface of the recording medium at a distance therefrom such that the focal plane of the projection lens coincides with the planes of said foci of either said concave or convex mirrors provided by the deformations, a screen, said projection lens imaging the planes of said foci of either said concave or convex mirrors on said screen.'

3. A projection system for projecting an image of infonnation stored on a recording medium in the form of surface deformations, said recording medium having a reflecting surface with substantially similar deformations forming concave mirrors with foci in planes in front of said medium and convex mirrors with foci in planes behind said medium, said system comprising a cabinet, means for supporting the recording medium at one end of said cabinet, means directing substantially collimated light to the reflecting surface of the medium,

a projection lens in the path of light reflected from said medium transmitting reflected light toward the opposite end of said cabinet, said projection lens being positioned along the path of reflected light a distance from said recording medium, such that the focal plane of the projection lens coincides with the planes of said foci of one of said either said concave or said convex mirrors provided by the deformations of said medium, means for redirecting the light towards said one end of said cabinet and a back projection screen on said one end of said cabinet for displaying the information recorded on said medium.

4. The system of claim 2 wherein said means directing substantially collimated light onto said medium includes a light source off the projection axis of the system and a mirror tilted with respect to the projection axis.

5. The system of claim 3 wherein both said recording medium and said redirecting means are adjustable with respect to said projection lens. 

1. A method of projecting information stored in a recording medium as a pattern of surface deformations including reflective surfaces with substantially similar deformations therein forming concave and convex mirrors, said concave mirrors having foci in planes in front of said medium and said convex mirrors having foci in planes behind said medium, said method comprising illuminating the reflective surface of said medium with substantially parallel light and imaging the planes of said foci of either said concave or said convex mirrors on an image area.
 2. A projection system for projecting an image of information stored on a recording medium as a pattern of surface deformations, said recording medium having a reflective surface with substantially similar surface deformations which form concave and convex mirrors said concave mirrors having foci in planes in front of said medium and said convex mirrors having foci in planes behind said medium said system comprising means for supporting the recording medium, means directing substantially collimated light to the reflecting surface, a projection lens positioned along the path of light reflected from the surface of the recording medium at a distance therefrom such that the focal plane of the projection lens coincides with the planes of said foci of either said concave or convex mirrors provided by the deformations, a screen, said projection lens imaging the planes of said foci of either said concave or convex mirrors on said screen.
 3. A projection system for projecting an image of information stored on a recording medium in the form of surface deformations, said recording medium having a reflecting surface with substantially simiLar deformations forming concave mirrors with foci in planes in front of said medium and convex mirrors with foci in planes behind said medium, said system comprising a cabinet, means for supporting the recording medium at one end of said cabinet, means directing substantially collimated light to the reflecting surface of the medium, a projection lens in the path of light reflected from said medium transmitting reflected light toward the opposite end of said cabinet, said projection lens being positioned along the path of reflected light a distance from said recording medium, such that the focal plane of the projection lens coincides with the planes of said foci of one of said either said concave or said convex mirrors provided by the deformations of said medium, means for redirecting the light towards said one end of said cabinet and a back projection screen on said one end of said cabinet for displaying the information recorded on said medium.
 4. The system of claim 2 wherein said means directing substantially collimated light onto said medium includes a light source off the projection axis of the system and a mirror tilted with respect to the projection axis.
 5. The system of claim 3 wherein both said recording medium and said redirecting means are adjustable with respect to said projection lens. 